What are the primary defects looked for in green coffee grading?

Green coffee grading is the essential bridge between farm-level processing and the final cup. The SCA classification system serves as a standardized language, yet it is often misunderstood as a purely aesthetic exercise. In reality, these defects are markers of specific failures in the supply chain: agronomic stress, improper fermentation, or poor storage conditions. Primary defects, such as 'full black' beans, often indicate severe fermentation issues or contact with the ground, while 'full sour' beans point to over-fermentation or poor drying practices. These are not merely visual flaws; they introduce chemical compounds that create harsh, ashy, or vinegary notes that no roasting profile can mask. Secondary defects, while less catastrophic, signal inefficiencies in milling or sorting. A common misconception is that grading is solely the roaster's responsibility. In practice, the most successful producers integrate these grading protocols into their own quality control, using them as diagnostic tools to refine their processing methods. By identifying whether a defect is caused by mechanical damage during depulping or biological damage from pests, producers can make targeted adjustments to their infrastructure. For the producer, grading is not just about meeting a contract specification; it is a feedback loop that directly influences the value of their harvest. When a lot is rejected for primary defects, it is rarely a failure of the bean itself, but a failure of the process that brought it to the drying patio.